Semen is the white/yellow fluid that comes out of the penis when a guy ejaculates.
It can be clear and watery or thick and yellow, but it’s often a mixture.
About 3% of the semen is made up of spermcells, 15-30% comes from the prostate and about 70% from the seminal vesicles.
How much semen is expelled during ejaculation varies, but it normally amounts to half a teaspoon to a tablespoon.
When semen ends up near the vaginal opening or in the vagina, the girl can get pregnant.

I masturbate a lot, at least twice a day. Will I still be able to have children later?
The past two days there has been blood in my semen. Is this a sign something is wrong?
When I masturbate, where do I leave my semen?
Where does all the semen go to when I don’t masturbate?

There are clots in my ejaculate. Is this normal?
After intercourse semen drips out of my vagina. What can I do to prevent this?
How does semen taste?